I use this website for weather: www.weatherbase.com

Note that VN an Sri Lanka are quite far apart, so little correlation between weather patterns. In VN,central VN is quite rainy in Nov (often flooding),but north and south are not.

We were in Sri Lanka in Nov a number of years ago - had a wonderful time and almost no rain. But statistically, Nov is rainy in Sri Lanka. Several people on this forum went to Sri Lanka in Jan when it was supposed to be drier and were beset by floods. So even using good data is no guarantee in these times of climate change. The cultural triangle area of Sri Lanka tends to be drier than some other areas.

Here is a link to our photos from our 2007 trip. If you click on my name you'll find my trip report. If you choose view by country at the top of this page "Sri Lanka" you will find a good number of reports in the last several years.

We were there in January 2011 when, as Kathie says, it was supposed to be the dry season. For the first 2 weeks we were (literally) knee deep in floods although things got a lot better for the last two weeks of our stay. The devastation caused by the floods was unbelievable with many areas totally underwater. Whilst there many people told us that over the last few years it had not been possible to predict the arrival of the monsoons as the weather patterns had changed so much.

Vietnam is a very long thin country and the topography means that you will find some decent weather most times of the year. Floods aside, even in the wet seasons in these palces it often does not rain all day and sunshine does happen. You often have teh advantage of greener landscapes, lower rates and, less crowded tourist sites. Click on my screen name for my TR